A wet month of May boosted runoff into portions of the Missouri River Basin, according to the U.S. Army Corps of Engineers.
“Large areas of Montana, North Dakota, Wyoming, eastern South Dakota, and eastern Nebraska received more than 200% of normal precipitation for the month of May,” the agency noted in its monthly new release on reservoir status. However, central South Dakota, western Nebraska, and eastern Colorado received as little as 25% of normal precipitation.
May runoff for the basin above Sioux City, Iowa, was 3.5 million acre-feet, 104% of average, the Corps said.
Currently, almost a third of the basin is experiencing abnormally dry or drought conditions with drought conditions expected to persist through the end of August, the Corps said. Soil moisture is below normal in Montana, North Dakota, eastern Wyoming, and Colorado and near normal in South Dakota and northern Nebraska.
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Thanks to cooler, wetter weather, 56% of the annual peak of mountain snowpack remained in the reach above Fort Peck Dam as of June 1.
Last month’s rainfall came as Fort Peck Dam was releasing more water than usual as part of a test to see if endangered pallid sturgeon can successfully spawn in the Missouri River below the impoundment.
Flows from the dam peaked on April 26 at 18,000 cubic feet per second to attract fish into the Missouri River. Since then, releases have declined to around 10,000 cfs to what is being called retention flows meant to keep sturgeon in the river.
According to Pat Braaten of the U.S. Geological Survey, 12 pallid sturgeon entered the river in response to the increased flows, but not all of them stayed. At last count there were still four female pallids in the river.
The dam releases will be boosted again on June 13 with a target to hit 22,000 cfs. Those high flows will continue for a couple of weeks.
John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division, said in a recent update he doubted the tests would produce any “ah hah moments.” Instead, the scientists have designed their research to see if there is a dam management scenario that would increase survivability of any juvenile fish born after the pallid sturgeon spawn.
During the flow test a number of monitoring activities are being conducted including lidar and aerial photography, physical surveys, cultural resource surveys and water quality sampling. In addition, 1-day old pallid sturgeon will be stocked below the dam so scientists can monitor their survival.
By the end of May, Fort Peck Reservoir was at an elevation of 2,231.6 feet, up .3 feet from April 30. By the end of June the lake is predicted to fall by almost a foot.
